Structures such as buildings, public works and the like are frequently produced from concrete by casting the concrete into a space defined between two walls or surfaces and permitting the concrete to harden therein. The form is constituted by so-called falsework, i.e. a structure which does not itself constitute the final load-bearing member of the structure and such forms or falsework can be of two types, namely, removable forms which may or may not be reused or so-called lost forms which remain in place in the structure after the concrete has hardened.
Lost forms can include insulating members which by their presence on and in the hardened concrete structure, contribute thermal or insulating properties to the structure which may be a wall. Of course, the lost forms can contribute other properties, e.g. weatherproofing, esthetic characteristics or the like.
When the lost forms are to provide insulating characteristics, the material from which the forms are constituted can be composed of insulation or insulating material.
The lost forms which have been provided heretofore generally can also be divided into two categories, namely those constituted by planar solid slabs and those formed by hollow parallelopipedal blocks.
The large planar slab units have not gained widespread acceptance because their dimensions are determinitive of the dimensions of the structure to be cast and frequently it is not possible to employ these slabs conveniently in building or other structures. Furthermore, the use of such slabs is complicated by the need to employ connectors between the slabs which are difficult to emplace. Furthermore, they generally do not have sufficient insulating capabilities especially at the extremities of a wall to be formed by casting concrete into the lost mold.
The second type of lost form, namely that which is composed of hollow parallelopipedal blocks can be utilized for a greater range of structures because they are emplaced simply by disposing one block next to another and stacking rows of blocks in an imbricating pattern. Such arrangements can be adapted to various architectural plans and designs. Nevertheless they too pose considerable problems.
For example, once the wall is formed, the connections between the blocks are formed by insulating material tending to melt or to be thermally destroyed in the case of fire, leaving openings in the concrete wall. These horizontal "conduits" can be of considerable diameter and create the danger of airflow and thus of transmission of fire.
The angles at which the blocks join are comparatively weak and weaknesses occur as well at the junctions between rows of blocks, i.e. because the horizontal joints between the concrete constitute one wall and the concrete constituting an adjacent wall constitute discontinuities.
The volumes of the blocks, moreover, create problems with respect to their transport and transport costs because the ratio of volume-weight is considerable. As a consequence, even such lost forms have not gained widespread acceptance.